PARIS — Air France has replaced the air speed sensors on its entire fleet of Airbus A330 and A340 long-haul aircraft, a pilots' union official said Monday. The company had been under pressure from pilots who feared the devices could be linked to the crash of Flight 447.

In the deep waters of the mid-Atlantic, a Dutch ship began trolling with a high-tech, U.S. Navy listening device Monday in search of the flight data and voice recorders. Investigators say information from those black boxes is key to determining what caused Air France Flight 447 to crash into the ocean with 228 people on board.

Experts looking into the May 31 crash of the 4-year-old Airbus A330 jet have so far focused on the possibility that external speed monitors — called Pitot tubes — iced over and gave false readings to the plane's computers.

In the weeks before the accident, Air France had begun replacing the tubes on its A330 and A340 jets, but not yet on the plane that crashed. After the accident, the airline pledged to speed up the switch and complete it by the end of this month, after pilots complained.

The whole fleet "is equipped since the end of last week with Thales' BA sensors," said Erick Derivry, a spokesman for the SNPL pilots' union. The crashed jet was equipped with the older AA model sensors, which Airbus has recommended airlines replace.

Defending the Airbus recordDespite questions about the performance of the Pitot tubes, Derivry stressed, "Today it is not proven or established that the AA model probes are at the origin of the accident."

Airbus CEO Tom Enders defended the A300 on Monday, as his company sought to sell more of the planes at the Paris Air Show.

"Their record is very, very impressive," he said. "(They have) more than 16 million flight hours, more than 3 million flights and this is so far one of the safest commercial aircraft built."

"We are supporting the investigation as much as we can and we very much hope that the recorders will be found soon, so that we find out what really happened," Enders said.

Concern about the crash clouded the Paris Air Show. Qatar Airways' head, Akbar al-Baker, said his airline in the process of replacing its Pitot tubes before the Air France crash.

An official of the French accident investigation agency, BEA, began examining some of the debris retrieved from the ocean in the Brazilian city of Recife. It was not clear, however, whether the BEA would continue analyzing the pieces in Brazil or have them shipped to France.

On the water, the U.S. Navy device, called a Towed Pinger Locator, was trying to detect emergency audio beacons, or pings, from Flight 447's black boxes, which could be lying thousands of feet (meters) below the ocean surface. The sounds begin to quickly fade 30 days after a crash.

The initial search area spans a 2,000-square-mile (5,180-square-kilometer) section of the Atlantic, said U.S. Air Force Col. Willie Berges, commander of the American military forces supporting the search.

Trolling in a grid patternThe Dutch ship is trolling in a grid pattern after talking with French military officials who are using nuclear submarine to hunt for the black boxes, Berges said. A second Dutch ship carrying another pinger locater was to arrive Monday afternoon.

"We have a limited amount of time to cover the search area," Berges said, but added that the ships towing the locators will continue searching even if no pings are detected beyond the 30-day timeframe.

So far, there is no evidence of an explosion or terrorist act in the crash, just clues that point to systemic failures on the plane. Experts say the evidence uncovered up until now points to at least a partial midair breakup of the plane.

French Ambassador Pierre-Jean Vandoorne, a liaison between the victims' families and authorities, said Monday he met in Recife with those in charge of the Brazilian recovery and their search teams are not scaling back.

"No date has yet been fixed regarding an eventual halt to the search at sea," he said on France-2 television. He said Brazilian and French aviators have already spent 1,000 flight hours looking for victims and debris.

Brazilian authorities say they have recovered 43 bodies and another six have been found by French ships.

Vandoorne would not comment on the nationality or any other details of the bodies pulled from the ocean. Coroners say victims' dental records and DNA samples from relatives will be needed to confirm the identities of the 16 bodies examined so far.

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